This application relates to motion measurement devices. More particularly, this application relates to an apparatus for measuring displacement of the wrist, capable of measuring displacement in both the radial/ulnar and flexion/extension planes.
It often is desirable to measure displacement of body parts when in motion. Such measurement may be useful in diagnosing injuries, such as loss of motion, and in studying repetitive motions to determine if such motions cause injury or strain. Knowing the position and displacement of body parts is important to biomechanical analysis. In clinical settings, motion measurement devices may provide information about motion pattern or range of motion. This knowledge may be used to determine the status of the is function of a body part and to guide treatment plans. Also, in the workplace, posture and repetitiveness of tasks may be measured. Some primary factors assessed in the workplace may include posture, force and temporal characteristics. Temporal characteristics may include the number and duration of rests and frequency of the motion. This knowledge may assist in assessing and redesigning tasks that may pose risk of injury.
Various systems have been developed for quantification of position and displacement of body parts, including active and passive cinematographic systems and electromagnetic field based systems. These systems are accurate. They tend, however, to be costly, require technical training to use, have certain technical limitations, and are generally not portable. Additionally, portable devices, such as wrist goniometer systems, require calibration for each user. For example, typically joint angular displacement at several points throughout a range are sampled, then linear regression or other techniques are used to estimate the relationship between position and transducer output. A wrist goniometer has been disclosed having two potentiometers with spring loaded cables. Individual calibration, however, is required through sampling multiple points in a range and using linear regression or similar techniques to estimate the relationship between position and transducer output.
U.S. Pat. No. 5,012,819 discloses an apparatus for monitoring the motion of components of a spine. The apparatus is mounted on the back of a patient, and includes an exoskeleton of elements which resemble the spinous process and transverse process of the spine. The elements include a central bore for receiving a cable, and three separate openings, each for receiving a wire therethrough. The cable is attached to a potentiometer which measures the twisting motion of the spine. Each of the three wires is attached to a separate potentiometer to measure flexing in the sagittal, transverse and lateral planes. The signals from the potentiometers are processed to provide a measurement of the angular position, angular velocity and angular acceleration of the spine as a function of time, for each of the three planes.
A wrist goniometer is provided that allows direct determination of wrist angular displacement in the radial/ulnar and flexion/extension planes without the necessity of extensive calibration or precise alignment relative to bone landmarks of the hand, wrist and forearm.
According to one embodiment, a goniometer is disclosed having a forearm component having at least three displacement measuring devices, and adapted to be releasably attached to a forearm of a user. A hand component is adapted to be releasably affixed to a hand of a user, and cables extending from the displacement measuring devices are adapted to be releasably connected to the hand component. The displacement measuring devices are configured to measure angular displacement of the hand component relative to the forearm component.
In one embodiment, the displacement measuring devices are configured to measure the angular displacement of the hand component relative to the forearm component on both a radial/ulnar plane and a flexion/extension plane. The cables may be under constant tension when the goniometer is in use. When the goniometer is in use on a hand and forearm of a user and viewed from above at least two cables may be substantially parallel to each other. When the goniometer is in use and on a hand and forearm of a user and viewed the side of the hand at least two cables may be substantially parallel to each other. When the goniometer is in use on a hand and forearm and viewed from the side the cables may be substantially parallel to a volar aspect of the hand and the forearm of the user when the hand and forearm are in a natural flexion position. At least first and second cables extending from the forearm component may be located at substantially the same height from a base of the forearm component. A third cable extending from a third displacement measuring device may be located at a height between the base of the forearm component and the first and second cables.
In one embodiment, at least one displacement measuring device is a potentiometer comprising a reel and a cable extending from the reel. At least the first and second cables extending from the first and second potentiometers may be located at substantially the same height from a base of the forearm component. A third cable extending from the third potentiometer may be located at a height between the base of the forearm component and the first and second cables.
In one embodiment, the hand component is a unitary piece. The cables may be releasably attached to the hand component allowing for unrestrained rotation. The hand component may include at least two pylons extending from the hand component for locating free ends of the cables. Swivel joints may releasably connect each cable adjacent a top of a pylon. A swivel joint may releasably connect a third cable to a base of a pylon. The hand component may further include a cross-member for locating the pylons on the hand component. The hand component may further include a bar for removably locating the cross-member. The bar may further include slots provided along its length, and the cross-member may include channels such that the cross-member slidably engages the bar. The cross member may be adjustably secured to the bar with at least one screw.
In one embodiment, the hand component further includes a glove for removably attaching the hand component to a hand of a user. The glove may be a palmless glove. The glove may be a fingerless glove. The hand component may further include a bar secured to the glove. The bar may be secured to the glove such that the bar is adapted for location adjacent a volar surface of a third metacarpal of a hand of a user when the glove is place on the hand of the user.
In another embodiment, the forearm component further includes a housing for mounting the displacement measuring devices. A cuff may be provided adjacent the housing and adapted for removable securement to a forearm of a user. The cuff may include at least one hinge adapted for adjustment to the forearm. The cuff may be adapted to adjust to a cross-sectional area enclosed by the cuff. The cuff may be lined with orthotic foam. The foam may be sculpted such that the foam is adapted to fit a radial and ulna of the forearm. The cuff may have a strap adapted to releasably secure the cuff to the forearm. The strap may be removably secured to the cuff with at least hook-and-loop fastener. The cuff may be a band. The band may be elasticized. The band may be a loop. The band may be formed into a loop using hook-and-loop fastener.
According to another embodiment, a goniometer is disclosed having a forearm component having at least three potentiometers adapted to be releasably affixed to a forearm of a user. A hand component is adapted to be releasably affixed on a back of a to hand of a user, and the potentiometers are adapted to be connected to the hand component. The potentiometers are configured to measure angular displacement of the hand component relative to the forearm component without calibration.
According to another embodiment, a method of determining wrist position in both flexion/extension and radial/ulnar deviation planes of movement is disclosed. The method includes the steps of providing a forearm component for locating three displacement measuring devices above a forearm of a user, providing a hand component on the back of a hand of the user, and connecting a cable from each displacement measuring device to the hand component. The displacement measuring devices are configured to measure angular displacement of the hand component relative to the forearm component in both the radial/ulnar and flexion/extension planes.
In one embodiment the method includes connecting the cables to the hand component such that they are under constant tension. The step of connecting may include locating at least a first and second cable at substantially the same height from a base of the forearm component. The step of connecting may include locating a third cable at a height between the base of the forearm component and the first and second cables. The displacement measuring device may be a potentiometer including a reel and a cable extending from the reel. The step of connecting may include connecting the first and second cables from the first and second potentiometers to the hand component such that the cables are located at substantially the same height from a base of the forearm component and are substantially parallel to each other. The step of connecting may include extending a third cable from the third potentiometer to locate the cable at a height between the base of the forearm component and the first and second cables such that the third cable is substantially parallel to at least one of the first and second cables.
In one embodiment, the step of providing a hand component includes providing at least two pylons for connecting ends of the cables to the hand component. The step of connecting may include connecting the cables to the pylons with swivel joints. The step of connecting may include attaching the cables to the pylons to allow for unrestrained rotation. The step of connecting may include providing a cross-member for locating the pylons on the hand component. The step of connecting may include removably locating the cross-member on a bar of the hand component. The step of connecting may include removably securing the cross-member to the bar with screws.
In one embodiment, the step of providing the hand component includes attaching the hand component onto a glove for removably locating the hand component on the back of a hand of the user. The step of providing the hand component may include locating the hand component such that it is adjacent the volar surface of the third medicarpal on a hand of a user. The step of providing the forearm component may include mounting the displacement measuring devices on a housing of the forearm component. The step of providing the forearm component may include securing the forearm component to a forearm of a user by a cuff. The step of providing the forearm component may include adjusting cross-sectional area enclosed by the cuff. The step of providing the forearm component may include releasably securing the cuff to a forearm of a user with a strap. The step of providing the forearm component may include releasably securing the cuff to a forearm of a user with hook-and-loop fastener.